1. Field of the Invention
This invention relates to color stabilized distillate fuel oils. More particularly, this invention relates to inhibiting color deterioration of distillate fuel oils, such as straight-run diesel fuel.
2. Description of the Prior Art
Various middle distillate fuel oils tend, with time, to deteriorate. Normally, straight-run diesel fuels are stable during standing. However, some straight-run diesel fuels that contain abnormally high levels of organic acid and sulfur containing species can be quite unstable and may deteriorate. This deterioration usually results in the formation of sediment, sludge, or gum and objectionable color deterioration during transportation and storage. This fuel oil deterioration is caused, in part, by the presence of oxygen in the storage tank containing the fuel oil. Resulting oxidation of the fuel oil manifests itself in the appearance of darker colors, gum and the like. Discoloration of distillate fuel oils is objectionable for various reasons, including customers' preference for light colored fuel oils because discoloration may indicate that deterioration has occurred.
Suggestions of the prior art for stabilizing fuel oils include U.S. Pat. No. 2,672,408, Bonner, which discloses the use of oil-soluble water-insoluble amines, the general formula of which can be represented as: N(R).sub.3, wherein R can be hydrogen or the same or different hydrocarbon radicals with at least one R being a non-aromatic hydrocarbon radical, for protection of particular blends of liquid hydrocarbons against discoloration. Also, U.S. Pat. No. 2,742,349, McCoy, discloses the use of arylamine antioxidants and sundry substances derived from the class of piperazines for protecting various organic materials from deterioration in the presence of oxygen. U.S. Pat. No. 2,945,749, Andress, discloses the use of a tertiary alkyl, primary, monoamine having from about 4 to 24 carbon atoms and in which the primary nitrogen atom is directly attached to a tertiary carbon atom, for inhibiting fuel oil deterioration in storage. U.S. Pat. No. 3,017,258, Pollitzer, teaches the use of the reaction product of an amine compound, having at least 12 carbon atoms and a straight chain of at least three carbon atoms attached to the nitrogen atom, with an epihalohydrin compound for retarding deterioration of burner oil. U.S. Pat. No. 3,049,414, Kruyff, discloses a process for stabilizing the color of gasoline comprising the steps of washing the gasoline with a liquid characterized as being free of heavy metals and capable of dissolving pyridine; washing with alkaline aqueous solution, characterized as being free of heavy metals; removing substantially all the free alkali; and then adding an organic nitrogenous base, all of whose carbon-carbon bonds are saturated. U.S. Pat. No. 3,129,699, teaches the use of heterocyclic polyamine salts of organic acids to improve the ignition characteristics of diesel fuel. Also, U.S. Pat. No. 3,198,730, Goodrich, discloses the use of a solid sulfuric acid catalyst composition for treatment of catalytically cracked hydrocarbon distillates boiling up to and including the gas oil boiling range.
Additionally, U.S. Pat. No. 3,490,882, Dunworth, relates to stabilized petroleum distillate fuel oils containing N,N-dimethylcyclohexylamine and, optionally, an N,N'-di(orthohydroxyarylidene)-1,2 -alkylenediamine. U.S. Pat No. 3,640,692, Rakow, et. al., discloses a stabilized distillate hydrocarbon fuel oil composition comprising a major proportion of a distillate hydrocarbon fuel and a minor proportion of a stabilizer comprising (a) an additive selected from the group consisting of (1) an amide plus a Schiff base; (2) an amide containing a Schiff base group; and (3) an amide containing a Schiff base group in combination with either an amide or a Schiff base; and (b) a cyclohexylamine selected from the group consisting of N,N-dimethylcyclohexylamine and dicyclohexylamine. Also, U.S. Pat. No. 3,701,641, discloses a stabilized distillate hydrocarbon fuel oil composition comprising a major proportion of a distillate hydrocarbon fuel and a minor proportion of a stabilizing additive comprised of (a) a polyamine having 2 to about 6 amino groups and containing about 24 to 50 carbons; (b) N,N'-disalicylidine-1,2-propylenediamine, and (c) a cyclohexylamine selected from the group consisting of N,N-dimethylcyclohexylamine and dicyclohexylamine. Of particular interest is U.S. Pat. No. 3,818,006, Klemchuk, which discloses the use of sundry substituted hydroxylamines for stabilizing diverse organic materials against oxidation. Additionally, U.S. Pat. No. 4,509,952, relates to an alkyldimethylamine ranging from C.sub.4 -C.sub.20 alkyl which may be added to a distillate fuel as a stabilizer to prevent fuel oil degradation. However, none of these prior art references disclose the unique and effective mixture of triethylenetetramine and N,N-diethylhydroxylamine for inhibiting color deterioration of distillate fuel oils.